The long term objective of this investigation is directed towards elucidating a potential mechanism whereby membrane-enzyme interactions may participate in the control of cell growth and proliferation. This objective encompasses studies concerned with the following three related problems: I. Factors controlling the synthesis, assembly and expression of the Moloney Leukemia Virus-Induced Surface Antigen (MCSA); II. Molecular differences in membranes from Epstein Barr virus (EBV) negative lymphoma lines and their in vitro EBV-transformed sublines; and III. Covalent surface modification of human lymphoid cell lines. Successful achievement of these studies will provide relevant information as to: 1) how MCSA, a tumor-specific surface antigen, is involved in the control and prevention of oncornavirus-directed tumors; 2) how an EBV directed membrane antigen (MA) may be related to the proliferative transforming interaction of virus and lymphocytes and 3) how the regulatory function of phosphorylation and sialylation of surface macromolecules may be related to somatic cell modification of MA. This may occur either by enhancing the turnover of MA from the cell periphery (an established event associated with recurrence of Burkitt lymphoma) or by a decrease in the immunogenicity of the antigen.